In the process for manufacturing stainless steel, which is a kind of metal, molten iron is produced by melting raw materials in an electric furnace, molten steel is obtained by subjecting the produced molten iron to refining including decarburization for instance performed to remove carbon, which degrades properties of the stainless steel, in a converter and a vacuum degassing apparatus, and the molten steel is thereafter continuously cast to solidify to form a plate-shaped slab for instance. In the refining process, the final composition of the molten steel is adjusted.
In the continuous casting process, molten steel is poured from a ladle into a tundish and then poured from the tundish into a casting mold for continuous casting to cast. In this process, a seal gas shielding the molten steel surface from the atmosphere is supplied around the molten steel transferred from the ladle in the tundish to the casting mold in order to prevent the molten steel with the finally adjusted composition from reacting with nitrogen or oxygen contained in the atmosphere, such a reaction increasing the content of nitrogen or causing oxidation.
For example, PTL 1 discloses a method for manufacturing a continuously cast slab by using an argon gas as the seal gas.